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Stock-Based Compensation (Summary of Unvested Stock Options) (Details) - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Shares      
Unvested, beginning of period (in shares) 50,833    
Granted (in shares) 32,750 0 50,000
Vested (in shares) (35,002)    
Unvested, end of period (in shares) 48,581 50,833  
Weighted Average Grant Date Fair Value      
Unvested, beginning of period (in dollars per share) $ 12.67    
Granted (in dollars per share) 11.93   $ 10.33
Vested (in dollars per share) 13.73    
Unvested, end of period (in dollars per share) $ 11.41 $ 12.67